The present invention relates to a door lock incorporating both a dead bolt and a push latch. Preferably, the device is enclosed in a housing which is relatively narrow so that it can be installed within the edge of a door, such as a security screen door or storm door which, in many instances, is produced from aluminum or other metal.
In the past, many such doors have been provided with rather flimsy locking structures which will hold the door closed for most purposes, but which can easily be defeated by anyone desiring to make an unauthorized entry. One such locking structure, for example, has comprised a detent structure which is fixed on the interior portion of a pivotable door handle. When the door closes, the detent structure pushes a complementary detent device out of the way. In many cases, this latter device comprises a spring-biased pin or bar which then snaps back into place as the detent portion of the handle continues to move past it as the door pivots to the final, closed position. When an occupant desires to open the door, he merely pivots the handle to a position in which the detent structure thereon rotates out of a position in which it can contact the pin. The locking structure for such doors has normally comprised a simple device which prevents the handle from being pivoted.
It is well known that locks of this type are relatively ineffective for prohibiting unauthorized entry. Similarly, it is well known that most police burglary departments recommend that doors be locked with a bolt having a minimum throw or extension out of the door of one inch. Obviously, locks such as this prohibit all but the most determined of unauthorized entries. Such locks have been shown (for example) in U.S. Pat. Nos. 2,380,708; 3,384,404; 3,626,507; 3,917,329; and 4,182,145.
Although there are locks available for such doors which are more secure than that prior art screen door lock described above, most of them have been manufactured in such a way that they must be relatively thick. This results in the lock having to be mounted on the exterior surface of the door with, in some cases, a key-actuated cylinder extending through a bore in the door (see, for example, U.S. Pat. Nos. 2,380,708; 3,626,507; and 3,917,329). Since many such doors are located very close to the main structural door of the entry within which they are mounted, it is sometimes quite difficult, if not impossible, to use such a lock since the two doors cannot be closed simultaneously. Also, the appearance is one of "add-on" hardware which leaves the impression of poor quality workmanship.
It is also desirable to have a lock which may be encased in a relatively thin housing which can be inserted into the edge of a rather thin door, such as an aluminum security screen door. Preferably, the lock would also include a push latch bar which will hold the door closed until a handle or doorknob is turned. Prior art push latches of this general type, although of rather complex structures, have been shown, for example, in U.S. Pat. Nos. 3,361,462 and 4,286,812. Still further, it is preferred that structure be provided to allow modification of the push latch operation so that the installer may carry a single lock in his inventory for use regardless of whether the door hinge is at the right or left hand side of the door.